The goal of this research is to improve understanding of the inner workings of mammalian retinas using combined electrophysiological, anatomical, and neurochemical approaches. A. Dopaminergic amacrine cells of monkey retina parallel rods in spatial distribution. Visualized in whole, flat mounted retinas using an aqueous, formaldehyde-induced fluorescence method, dopaminergic amacrines can be observed everywhere in monkey retina outside the foveal pit. Their density is non-uniform, however, being minimal in foveal and peripheral regions and maximal at 3 mm eccentricity, the region of peak rod density. There are about 7500 such cells per retina. Dopamine may thus be associated with rod-system function. B. Al7 amacrine cells of cat retina depolarize in sustained fashion and have the spectral sensitivity of the rods. Revealed by intracellular recording, HPR injection, light and electron microscopy, Al7 cells receive input only from rod bipolars and other amarine cells, among them the dopamine containing amacrine cell of cat retina. Al7 is about 800 um in both dendritic and receptive field and broadly stratified in the cat inner plexiform layer. C. Al9 amacrine cells of cat retina are rare types with transient, on-off depolarizations. Wide in dendritic field and narrowly stratified in s2 these receive input from cone biplars and (primarily) other amacrines, but not dopaminergic amacrines. D. Biplexiform cells in monkey retinas are unique ganglion cells that send dendritic processes to contact rods directly. Intracellular recording and staining of such a cell in Macaca fascicularis has revealed a depolarizing on-off waveform, a broad receptive field, and activation by both rod and cone mechanisms. The axon traveled through the inner plexiform layer for 0.3 mm before descending to the optic nerve fiber layer and changing course to proceed to the optic disk.